What is the general consensus when a question is answered but no up vote nor "accepted" is left by the OP? For a site that is based on reputation is it incorrect for the author to the answer to request an "accepted" or up vote from the OP? I've noticed several times (especially with first time asker's) that an OP will comment with a "thank-you" or "this is what I will do", but nothing more.
It seems to me that a lot of these questions come from new users, who won't necessarily understand the how Stack Exchange sites work or have the ability to vote yet. (If you're feeling curious, take a look at the profile page to see if the have the Informed badge, which says if they've read to the bottom of the tour page).
In my opinion, there's nothing wrong with leaving a comment asking them to accept the answer if you do it in a way that guides the user towards understanding both what they should do and why they should do it. There's a page in the help center that you can link to that explains it nicely: What should I do when someone answers my question?
So, if the OP leaves a "Thank you, this fixed it" comment, reply with something like*:
If this answer was useful to you, please consider clicking the check mark on the left to accept it to indicate that your problem has been solved. Please see the help center for more information about accepting an answer.
If you do leave a comment like this, be sure to delete it if and when the OP does accept the answer. You can also consider flagging their "Thank you" comment too since the accept is a better signal that the answer was helpful.
* As opposed to:
If this answer was useful to you, please accept it.
which may leave them confused because they just said in the previous comment that they accepted it.
This is a common issue amongst ALL SE sites, and the answer from the powers that be is that there is nothing that should be done by mods or the powers that be. See the overall Stack Exchange answer on the Meta.SE Question Moderators accepting answers on user's behalf after a certain time period
Accepting an answer has been, and will always be, up to the asker.
No, this is a user-oriented site. It is intended to answer people's questions. They know their problem the best and know what solves it for them. We need to leave it up to them to accept whatever answer they want. People will know what the community agrees with by the upvotes. The power to accept an answer should stay in the user/asker's hand. That way you have both opinions/views in a question.
The only thing that can be done is what @NiallC has suggested, to poke the asker with a comment on what they should do.